Introduction: Vitamin D deficiency is one of the most important medical problems, especially in children. It seems that one of the factors related to vitamin D deficiency in children is weight and obesity. The purpose of this study is to investigate the frequency of vitamin D deficiency in obese and non-obese children referred to Ali Asghar Zahedan Clinic in 1402. Materials and methods: In this study, 94 children referred to Ali Asghar Clinic in Zahedan, including 47 obese children with high body mass index and 47 non-obese children with normal body mass index in terms of vitamin D levels. They were investigated in 1402. The samples were selected as available. The data was collected using observation and examination and experiments. Data analysis was done in SPSS version 22 software using independent T and Chi-square statistical tests. A significance level of less than 5% was considered. Results: This study showed that the average vitamin D in two groups of obese and normal weight children was 21.7 ± 8.06 and 27.4 ± 12.4 ng/ml, respectively, and the level of vitamin D in obese children was It is significantly less than children with normal weight (P=0.011). Chi-square test also showed that the distribution of low vitamin level is significantly higher in the group of obese children than children with normal weight (14.9% vs. 6.4%) (P=0.05). Discussion and conclusion: This study showed that obese children and adolescents are more at risk of vitamin D deficiency, which can be caused by poor nutritional status in these children. It is suggested to do more research to find the causes of vitamin D deficiency and to prevent and treat it with vitamin supplements.